1. Field of the Invention
The present invention relates to a guide table device, and particularly, to an improvement of the guide table device capable of realizing compact and light-weight structure while maintaining high rigidity and high guiding performance.
2. Background Art
In a conventional technology, there is known so-called a build-up type guide table device utilizing a linear guide as a device freely moving a work table of a machine tool or like in X- and Y-directions which are perpendicular to each other. In such guide table device, a track rail is disposed, along the X-direction, on a base such as bed or column, a lower-side table is disposed to be movable along the track rail, a further track rail is disposed on the lower-side table to be movable along the Y-direction, and an upper-side table is also disposed to be movable along the further track rail. Accordingly, in such guide table device, the upper-side table is freely movable in the X- and Y-directions with respect to the base (for example, refer to Patent Publication 1).
Further, Patent Publication 2 shows another guide table device intended to provide a compact and light-weight structure by press-working a thin steel plate. In such guide table device, lower-side plate and upper-side plate are formed in shape of channel by bending both end portions of the steel plates through press-working, and an intermediate portion is also formed by bending downward opposing two sides of surrounding four sides and bending upward remaining opposing two sides in a manner such that the bent opposing side wall portions constitute the upper-side plate, the lower-side plate and the intermediate portion, and a plurality of balls are disposed between the mutually opposing side wall portions, the balls rolling along the side wall portions, so that the intermediate portion is moved in the X-direction with respect to the lower-side plate, and the upper-side plate is moved in the Y-direction with respect to the intermediate portion.
Furthermore, Patent Publication 3 discloses a guide table device which is capable of being moved in a rotating direction (θ) as well as horizontal direction (X- and Y-directions). The guide table device shown in Patent Publication 3 realizes the movement in the X-, Y- and θ-directions in combination of a cross-perpendicular guide and a bearing.
Patent Publication 1: Japanese Patent laid-open Publication No. HEI 11-280761
Patent Publication 2: Japanese Patent laid-open Publication No. HEI 5-18415
Patent Publication 3: Japanese Patent laid-open Publication No. HEI 9-243766
However, in the guide table device disclosed in the above Patent Publication 1, the Y-directional track rail is disposed on the lower-side table movable in the X-direction, and accordingly, the lower-side table requires itself a high rigidity, and in addition, a height from a stationary portion to the upper-side table becomes long, thus providing a problem of large size and heavy-weight structure.
The guide table device disclosed in the above Patent Publication 2 realizes a compact and light-weight structure. However, in this guide table device, the lower-side plate, the intermediate portion and the upper-side plate are formed of thin steel plate through press-working, and accordingly, if the press-working is carried out with less performance, a gap will be formed between the ball and a ball rolling groove, which results in a saccadic movements of the intermediate portion to the lower-side plate and of the upper-side plate to the intermediate portion, and hence, the upper-side plate cannot be moved at high performance with respect to the lower-side plate, thus being inconvenient.
With the guide table device of the Patent Publication 2 mentioned above, the gap between the ball and the ball rolling groove may be eliminated by selecting balls each having a slightly larger diameter and imparting a preload to the ball rolling on the ball rolling groove, and the generation of the saccadic movement of the upper-side plate with respect to the lower-side plate may be prevented. However, in such device, since ball rolling groove is formed by the side wall portions bent by the press working, when the large-diameter balls are selected, the ball contacts the ball rolling groove and the side wall portions of the respective plates are hence deformed before the compression. Accordingly, a sufficient preload is not applied to the balls, being also inconvenient.
Because of the reasons mentioned above, in the guide table device of the Patent Publication 2, it is required to improve the working performance in the press-working and increasing rigidity of the steel plate forming the respective plates. However, these requirements decrease a merit in the press-working, i.e., good productivity or low cost, and increase manufacturing cost of the guide table device.
With the guide table device which carries out the guide only in the X- and Y-directions, some disadvantages or inconveniences mentioned above are provided, and in a case of additionally performing the guiding in the θ-direction, it is inevitable to further increase the size and weight of the device. For example, in the guide table device disclosed in the above Patent Publication 3, a shaft member is disposed above three cross-perpendicular guides, and a table is provided via a bearing mounted to this shaft member. Accordingly, the guide table device of the Patent Publication 3 has a large size in both the vertical and horizontal directions for accommodating structural members, thus increasing the manufacturing cost.